New wave of Shylock Trojan targets bank customers

Cybercrooks wielding the Caphaw (better known as Shylock) banking Trojan are once again targeting users of financial institutions around the world, warns Zscaler.

The initial infection vector is currently unknown, but the researchers are almost positive that the malware is served by an exploit kit that takes advantage of Java vulnerabilities found on the targets’ computer.

“The reason we suspect this is that the User-Agent for every single transaction that has come through our Behavioral Analysis solution has been: Mozilla/4.0 (Windows XP 5.1) Java/1.6.0_07,” they pointed out.

The variation in the dropped executable is different across every instance, so at the time of the research the files have had an abysmal detection rate (1/46 at VirusTotal, currently 25/48).

The malware is very insidious. “Caphaw avoids local detection by injecting itself into legitimate processes such as explorer.exe or iexplore.exe, while simultaneously obfuscating its phone home traffic through the use of Domain Generated Algorithm created addresses using Self Signed SSL certificates,” they explained. “This limits the ability of traditional network monitoring solution to dissect the packets on the wire for any malicious transactions.”

Before attempting to run itself, the malware checks to see if it is running in a VM environment and whether the host is connected to the Internet. If the answer to the first question is Yes and to the second one No, it won’t even attempt to run.

The quasi-random domain names generated function as C&C servers which the malware contacts for instructions and to which it sends the stolen data, and the communication is encrypted.

These variants are targeting the customers of 24 different financial institutions mostly located in the US and Europe, including Barclays Bank, Bank of America, Chase Manhattan Corporation, Intesa Sanpaolo, Banco Mercantil, Wells Fargo Bank, Bank of Scotland, and others.